I'm guessing I'd need to keep 1.25" of meat at the bottom to give room from the spring clip and adjuster. That'll leave 1.75" to centre allowing a 3.5" maximum dia wheel. That would be a substantial wheel. Length wise, at 175mm - that's just short of 8" - having 1.5" sides also would give a distance of 5", about 100mm maximum distance between runners I.e max pivot size. Any thoughts?

So why can't the hinge part of this just be a piano hinge all it does is open up.? The acuracy to me would be in the shaft suports and if there is enough room to drill and ream for the spring tension in the shaft to hold the gears.

So why can't the hinge part of this just be a piano hinge all it does is open up.? The acuracy to me would be in the shaft suports and if there is enough room to drill and ream for the spring tension in the shaft to hold the gears.

It can be any kind of hinge as long as it is parallel to the axles - it is ensuring the alignment of all the parts that is critical.

Yes, the bigger the hinge balls the larger the opening (although this also requires a bigger diameter spring)

ATM I am experimenting with a 15mm ball. This gives it a 66mm axle spacing (not much point in holding one large gear only)

I've been looking around at bull dog clips the largest standard type clip (70mm wide) has a maximum throat of 17mm (the spring would probably open to 20+), which is a bit too small even with small ball hinges.

The commercial Webster design gives a maximum 3 3/4" swing between axel centres but this is generally bigger overall than this one. I appreciate practically it'll work but aesthetically odd! Also, it may be tricky holding smaller wheels if placed on the outside.

Bill - what opening does that give? Thinking about it, the opening would have to be larger than the maximum wheel diameter radius. Otherwise, the depth would allow you to fit the wheel on but if you couldnt space it to the radius, you could not mesh it with a pinion.

Hmmmm, felt like I kind of stalled the discussion. Too bad and not my meaning. To try to illustrate what I was after, I quickly made a 2D sketch.It is based not on a ruler but on two bars, say about 6 mm dia and some various sized brass blocks about 25 mm high and 10 mm thick. Should be sturdy enough. Thickness probably OK if 8 mm.

The two end pieces are pinned to limit the risk for twisting. At the right end the end block is wider and carries one of the depthing pegs. The other larger block slides sweetly on the bars without any slop at all. This block carries the other depthing peg.

To achieve a micrometer adjustment, the smaller moving block to the left of the left peg block, has a locked in thumb screw working into a thread in the adjacent peg block. With a spring between them it will be easy to adjust minutely the gear centres.

Locking the depthing pegs is done like a height gauge and locking the peg block and adjustment block is done using a cross "bar" nipping the slide rods like the arm locks on a GHT pillar tool.

This would be easy to make and if the rod holes are drilled and reamed before parting the brass bit, the distances will be exact. Probably simple to make as well.

I thought that the depthing pegs shall allow to insert a 2mm? gear axle at the top to fit the gears on, and then when marking exchange the 2mm pins for a piece of say 5/2 mm extension piece to tap upon.

Much like the image on page 1 of this thread where the depthing pegs goes bweteen the "bars" 90 degrees compared with my sketch.

I thought that the depthing pegs shall allow to insert a 2mm? gear axle at the top to fit the gears on, and then when marking exchange the 2mm pins for a piece of say 5/2 mm extension piece to tap upon.

Much like the image on page 1 of this thread where the depthing pegs goes bweteen the "bars" 90 degrees compared with my sketch.

Hi guys and hi Bill, I know you have been putting a lot of effort into helping me here. I'm actually moving - it's all happened unbelievably quick and although we still have a good number of weeks until move day, getting the workshop in storage was priority as everything is so heavy and I happened to have some storage offered to me! I genuinely went and purchased that 1/4" brass and then the next day turned the power off to my machines and now they are gone!

I can assure you, this will be the first project on the list when I get going again.....whenever this may be!

In the mean time I keen to get a plan in place and continue with the discussion!

Although I have nothing to do with clock making, this thread is of great interest and value. I am enjoying the development process! I wish I had a use for a Gear Depth Tool, it looks like a satisfying build.

OK, some sketching later. To begin, I did some more thinking about the micrometer adjustment screw and changed the design as shown at B in the sketch below.This way I can use an ordinary thumb screw and keep it tight using a spring between the thumb screw runner and the depthing peg runner.

When it comes to locking the runners to the bars I would use the same type of lock as I used on the bed stop for my lathe.The distance setting pin is locked using an intersecting "bolt" secured with a thumb nut. The works is shown below.I think it is easy to see which is the locking "bolt" in the picture.

I think this type of lock is good. Easy to handle and locks with strength.